1. Field of the Invention
The present invention relates to a miniaturized sealed lead-acid storage battery enclosed in a monoblock container and having no fluid electrolyte.
2. Background Art
As portable devices and appliances have been developed and used widely, the demand for seal lead-acid storage batteries increases. Recently requirements for the miniaturization, for improvement in energy density and for the reduction in cost have become particularly strong.
Conventionally, a battery has been produced in such a manner that plates are cured and dried after being filled with paste and are formed and dried according to demand to thereby obtain a group of plates. The thus obtained plates are inserted into an injection-molded battery container, the cells are connected to each other, and then a cover is joined with the battery container. In this case, it has been difficult to reduce the battery in size as well as its thickness because of the two steps of molding the battery container and inserting the group of plates into the battery container. That is, in the molding step, an internal mold of a core may be displaced by a pressure of molten plastic in injection-molding in the case where the internal mold is thin. In the insertion step, it is difficult to insert a thin element into the battery container through a thin opening portion.
Further, there has been proposed a single cell battery constituted by joining two halves of a bisected battery container. Each of the halves have such an arrangement that a plate-like current collector is fixed to the half of the battery container and an active material is closely attached to the current collector. In this design, however, there disadvantages have arisen that not only is it difficult to maintain the adhesion between the current collector and the positive active material, but in the case where a power load of a portable apparatus or appliance requires 6-12 volts, it becomes necessary to provide three to six cells so that the connecting portions between terminals and cells become large in mass and bulk with an accompanying reduction of energy density.